Optimization of Spent Coffee Grounds as Fat and Flour Substitutes in Gluten-Free Cakes: Effects on Quality...

With the increasing global population and the depletion of natural resources, there is a growing interest in alternative food sources with beneficial and functional properties. Spent coffee grounds (SCGs) stand out among food waste due to their rich nutritional composition and potential for evaluation in terms of a sustainability perspective. In this study, the objective was to determine the optimum utilization level of SCGs as a rice flour and fat substitute in gluten-free cake formulations. Response surface methodology (RSM) was employed to determine the optimum formulation to produce gluten-free cakes with SCG substitute. The effects of SCG substitution on fat content (0%, 20%, 40% [w/w]) and rice flour content (0%, 25%, 50% [w/w]) were investigated in terms of chemical, physical, and sensory properties of gluten-free cakes. The addition of SCG was found to significantly influence the substitution levels of fat and rice flour (p < 0.05). The optimum values for the independent variables were found as 36.75% fat substitute and 12.38% rice flour substitute. The optimum formulation confirmed the adequacy and predictive capability of regression models. In the optimum formulation of gluten-free cake substituted with SCGs, the baking loss was found to be 9.37%, L*_crust and b*_crust values were 43.87 and 8.06, both springiness and cohesiveness values were 0.18, total phenolic content was 1.11 mg GAE/g, antioxidant activity value was 1.59 mg TEAC/g for DPPH assay and 0.78 mg TEAC/g for ABTS assay, and overall acceptability was 6.75. Also, the addition of SCG resulted in approximately a 7-fold increase in dietary fiber content (from 2.3 g/100 g to 15.71 g/100 g). It is anticipated that gluten-free cakes formulated with SCGs may serve as an alternative product for individuals with gluten sensitivity and raise awareness about the valorization of food waste. The recovery of food by-products and the development of functional food products are expected to play a key role in the sustainable food technologies of the future.